1. Field of the Invention
The present invention relates generally to suspension systems for hard disk drive systems. More specifically, the present invention relates to providing tooling features integral to the suspension system to aid in forming suspension system components. The invention relates most specifically to forming anvils on a suspension system baseplate for pre-load forming of suspension system springs.
2. Related Art
Suspension systems for suspending read/write heads in hard disk drives (HDD) are well known in the art. In a typical HDD suspension system, the read/write head is mounted on a slider having an aerodynamic design, such that airflow between the slider and a spinning disk generates lift that allows the head to fly above the disk surface an optimal distance for reading data from the surface or writing data to the surface. The slider is typically bonded to a flexure (or gimbal), which permits the slider to pitch and roll as it tracks fluctuations in the disk surface. The flexure is coupled to a load beam, which is formed from a metal such as stainless steel and configured with a spring portion that applies a loading force, also known as a “pre-load” or “gram force”, to counteract the lift. A rigid end of the load beam is coupled to a baseplate, where an actuator is provided for precisely positioning the read/write head through actuation of the load beam.
The spring portion of the load beam is a linear flex-spring, or planar cantilever-type spring, typically formed from a metal sheet. The desired pre-load force is achieved by forming one or more bends in the linear spring portion of the load beam, taking into account the spring constant of the material, its mass, and the expected load. FIG. 1 illustrates a typical suspension assembly 100 consisting of a baseplate 102, springs 104, and load beam 106. In one commonly practiced technique, during manufacture of the assembly 100 springs 104 are preloaded using appropriate forming tools, such as tooling anvil 108 and roller 110. Springs 104 are bonded to the underside of baseplate 102 and load beam 106 to allow for placement of tooling anvil 108 at an optimal bend location 112 beneath the springs. So located, a bendable area 114 of each spring 104 is bent around a corner 140 of tooling anvil 108 under pressure of roller 110 as it pushes downward and rolls away from baseplate 102 in the directions shown by dashed lines. The resulting bend angle radius of spring 104 is therefore influenced by the curvature of corner 140. This curvature will change over time after repeated use of tooling anvil 108. Eventually, tooling anvil 108 will need to be replaced to avoid out-of-tolerance formation of bend angle radius in springs 104.
The main problem with the foregoing technique is that the accuracy of the bend location depends on placement of tooling anvil 108 with respect to assembly 100. HDD suspension systems typically demand very strict manufacturing tolerances on the order of 1.0 mil; therefore anvil placement requires high precision tooling, which adds to the manufacturing expense.
Another problem with the conventional anvil-and-roller technique is illustrated in FIG. 2, which shows a side view of a typical suspension assembly 200. Assembly 200 essentially consists of the same components as in assembly 100, except that a bridging area 214 of spring 204 has a shorter length relative to the diameter of roller 210. In suspension assemblies having this dimensional constraint, it may be impossible to impact roller 210 at the optimal bend location 212 due to mechanical interference from baseplate 202 or load beam 206. Where springs are bonded to the underside of the assembly, interference occurs as roller 210 encounters baseplate or load beam steps located above the surface of the spring. The example assembly 200 illustrates this interference effect: placement of roller 210 is limited by the step of baseplate 202 such that impact point 216 is displaced from optimal bend location 212 by a horizontal offset A. An excessive offset results in formation of the bend in a non-optimal location, or creation of an undesirable secondary bend.
In view of the foregoing, there remains considerable margin for improving pre-loading techniques for disk drive suspension assemblies.